This invention is directed to an artificial tissue as well as artificial organs, parts of organs, or systems of organs and also the use of artificial tissues or artificial organs for surgery training.
Artificial organs, parts of organs, or systems of organs for teaching purposes in the field of anatomy have been known for many decades. However, there are no artificial organs, parts of organs, or systems of organs which can be used for training in respect of special diagnostic and/or interventional procedures such as, for example, surgical high-frequency procedures or the like.
However, training with artificial organs, parts of organs, or systems of organs is extremely important particularly in the field of rigid and flexible endoscopy in order to allow one to learn how to safely manipulate the endoscopic instruments.
It is well known that endoscopic surgical procedures such as, for example, endoscopic polypectomy and the transurethral resection of the prostate comprise a relatively large number of variable and interdependent parameters so that comprehensive training is most important to the safe use and to avoiding complications in case of such surgical procedures.
An important parameter with all surgical procedures making use of high-frequency surgery resides in the high-frequency power the intensity of which is decisive both for coagulation and for operating. Adjusting the respective power and guiding the surgical instrument require experience and skill which can only be acquired by corresponding training.
Coagulation means the application of electrical high-frequency a.c. current for endogenic local heating of biological tissue, heating being employed up to a temperature at which intracellular and extracellular colloidal constituents of tissue undergo sol-gel-transformation. Any additional heating of the coagulated tissue will result in drying up, i.e. desiccation, whereby the volume of the tissue shrinks. Further heating of the desiccated tissue leads to carbonization, i.e. combustion. The aforementioned three thermally induced stages of necrosis differ from each other merely by the amount of heat required for each stage.
This already shows that substantial experience is required for a person to be able to successfully employ the desired technique. As an example, in some cases coagulation will suffice for efficient hemostasis while in others desiccation will suffice. Cutting by means of surgical high-frequency procedures requires the supply of energy in such a way that endogenic heating of the biological tissue is effected selectively and quickly up to a temperature at which intracellular and extracellular water is vaporized at such speed that the cell membranes will burst due to the sudden vapor pressure.
Additional difficulties will arise when, in the field of gastroenterology, coagulation procedures are to be performed by means of argon plasma with the aid of endoscopic instruments.
It is therefore the object of this invention to provide an artificial tissue as well as artificial organs which effectively permit realistic training directed to the handling of surgical procedures.
It is the basic concept of this invention to provide an artificial tissue which, on the one hand, exhibits suitable electrical conductivity so that the physical effects will occur which allow cutting during high-frequency surgery while water to be vaporized is still bound within the tissue, and on the other hand means are provided which are equal to solid organic tissue constituents so that combustion thereof will be possible analogous to natural tissue.
Moreover, in accordance with the basic concept of this invention the artificial tissue is capable of being shaped so that natural organs, parts of organs, or systems of organs may be modeled.
In accordance with this invention the use of shape-retaining hydrogels is proposed for the artificial tissue. Additionally, an electrolyte as well as combustible fibers, for example cotton or the like, are added to the mixture for forming the tissue.
Natural tissues having different structures or structural distributions may be modeled due to the fact that, in accordance with a further basic concept of this invention, different mixing ratios of the above listed ingredients may be realized, and different artificial tissues based on different mixing ratios may be combined within a tissue structure.
In one embodiment colorants are added to the artificial tissue so that an appearance may be obtained which corresponds to the natural tissue. Advantageously, colorants are employed which exhibit one or more color changes at one or more different defined temperatures, for example at the temperature at which natural human tissue will coagulate thermally. Advantageously, thermocolors are employed which undergo a change of color within the temperature range of from 50 to 100xc2x0 C. It is thereby possible to observe and control the temperature development in the artificial tissue during and after a cutting and/or coagulation procedure.
When artificial tissues are employed which exhibit one or more temperature-dependent changes of color, these may be used in the training of cutting effects, on the one hand, but also in the training of thermal coagulation procedures such as, for example, monopolar or bipolar contact coagulation, argon-plasma coagulation and laser coagulation.
In accordance with a further basic concept of this invention a hygroscopic agent such as glycerol is added to the mixture for forming artificial tissues so that undesirable premature desiccation is inhibited. Moreover, the admixture of glycerol improves combustion of the fibers contained in the tissue. Likewise, the admixture of preserving agents known from food chemistry to suppress mold growth is advantageous.
In accordance with this invention it is possible to shape organs, parts of organs, or systems of organs from the artificial tissues, which may be used not only to represent the anatomy and pathological changes but also for training purposes in the field of surgical interventions.
This enables the surgeon to recognize the respective pathological changes such as polyps, tumors, ulcers etc., on the one hand, and also to surgically treat or remove such pathologic changes in training, for example by cutting, coagulating, vaporizing, argon-plasma coagulating, and laser application.
A specific embodiment of this invention is based on the feature that vascular structures and body cavities may be formed in the artificial tissues to be filled with X-ray contrast media, concrements, liquids or gases so as to permit training of diagnostic procedures such as imaging procedures as well as combined procedures such as papillotomy or stone extraction. Artificial body cavities of this type are also used for training purposes concerning endoscopic surgery procedures making use of high frequency.
To summarize, this invention has succeeded in providing an artificial tissue which particularly in the case of cutting or coagulation by means of high-frequency current and laser application shows effects that are very similar to those occurring in natural human tissue.
Due to the electrical conductivity it is possible for high-frequency current to flow whereby endogenic heat is generated. This in turn leads to the formation of vapor resulting in desiccation. Since the hydrogels employed undergo gel-sol transformation, i.e. melt at elevated temperatures and the admixed combustible fibers can be cut only at a sufficient high-frequency voltage so that an electric arc will be formed between the cutting electrode and the tissue, effects may be obtained which are similar to the behavior of solid organic tissue components.
Below, this invention will be explained in detail with reference to an embodiment thereof.